The exhaust systems of today's automotive vehicles that are powered by internal combustion engines are typically equipped with catalytic converter systems. For maximum effectiveness, such catalytic converter systems must be heated to certain elevated temperatures. Since such heating typically comes from exhaust gases that pass through the catalytic converter, there exists an inherent time lag in the catalytic converter reaching maximum effectiveness upon cold engine starting.
In order to accelerate the effectiveness of the catalytic converter system at cold engine starting, it has been proposed to employ a close-coupled catalyst through which the exhaust gases are initially passed until the main catalytic converter has warmed up. A typical configuration comprises the parallel combination of a close-coupled catalyst and an exhaust control valve between the engine exhaust manifold and the inlet of the main catalytic converter. The exhaust control valve is normally open, but is remotely operated closed at engine starting to cause the exhaust flow to pass through the close-coupled catalyst before it enters the main catalytic converter. Since the close-coupled catalyst is capable of becoming effective sooner than the main catalytic converter, the catalytic converter system is rendered capable of becoming effective sooner than if equipped with only the main catalytic converter. Once the main catalytic converter has been heated sufficiently to attain proper effectiveness, the exhaust control valve is remotely operated to revert to its normally open condition. The exhaust gas flow takes the now-favored least restrictive path through the exhaust control valve directly to the main catalytic converter, rather than passing through the close-coupled catalyst before entering the main catalytic converter.
The exhaust control valve is exposed to a rather harsh environment, both thermally and chemically. Moreover, reliability requirements for the exhaust control valve are becoming more stringent. Accordingly, there is a need for improvement in the exhaust control valve that will enable automotive vehicle manufacturers to meet these more stringent requirements in a reasonably cost-effective manner. It is toward a solution for this need that the present invention is directed.
While the inventive features will be described and claimed with greater particularity hereinafter, it may be generally said that the invention relates to an improvement in the manner of sealing the journaling of the valve shaft on a wall of the valve body so as to prevent the escape of exhaust gases through the journal bearing that is mounted in the valve body wall and that journals a portion of the shaft that is between an interior portion of the shaft to which a valve blade is attached and an exterior portion of the shaft to which an actuating mechanism is attached, while still assuring reliable operation of the valve over its expected life. Still speaking somewhat generally, the invention comprises a novel association of a metal bellows with other metallic and non-metallic parts. The non-metallic parts are ceramic thrust washers. One embodiment of the invention provides for improved sealing of the valve blade to the wall of the valve body when the valve is closed by having the shaft axis non-perpendicularly intersecting the axis of the valve body wall, and the entire circumference of the valve blade provided with a circular ring seal. So that the detailed description of a presently preferred embodiment of the invention may now proceed, it is appropriate to briefly describe the accompanying drawings to which the description will make reference. These drawings illustrate the best mode presently contemplated for carrying out the invention.